Influence of Vesicular-Arbuscular Mycorrhizal Fungi on the Response of Potato to Phosphorus Deficiency

Abstract

Morphological and biochemical interactions between a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus fasciculatum [Thaxt. sensu Cerdemann] Cerdemann and Trappe) and potato (Solanum tuberosum L.) plants during the development of P deficiency were characterized. Nonmycorrhizal (NM) plants grown for 63 d with low abiotic P supply (0.5 mM) produced 34, 52, and 73% less root, shoot, and tuber dry matter, respectively, than plants grown with high P (2.5 mM). The total leaf area and the leaf area:plant dry weight ratio of low-P plants were substantially lower than those of high-P plants. Moreover, a lower shoot:root dry weight ratio and tuber:plant dry weight ratio in low-P plants than in high-P plants characterized a major effect of P deficiency stress on dry matter partitioning. In addition to a slower rate of growth, low-P plants accumulated nonreducing sugars and nitrate. Furthermore, root respiration and leaf nitrate reductase activity were lower in low-P plants than in high-P plants. Low abiotic P supply also induced physiological changes that contributed to the greater efficiency of P acquisition by low-P plants than by high-P plants. For example, allocation of dry matter and P to root growth was less restricted by P deficiency stress than to shoot and tuber growth. Also, the specific activities of root acid phosphatases and vanadatesensitive microsomal ATPases were enhanced in P-deficient plants. The establishment of a VAM symbiosis by low-P plants was essential for efficient P acquisition, and a greater root infection leve1 for Pstressed plants indicated increased compatibility to the VAM fungus. By 63 d after planting, low-P VAM plants had recovered 42% more of the available soil P than low-P N M plants. However, the VAM fungus only partially alleviated P deficiency stress and did not completely compensate for inadequate abiotic P supply. Although the specific activities of acid phosphatases and microsomal ATPases were only marginally influenced by VAM infection, VAM roots characteristically had a higher protein concentration and, consequently, enhanced microsomal ATPase and acid phosphatase activities on a fresh weight basis compared with N M roots. Morphological and ultrastructural details of VAM plants are discussed i n relation to the influence of the VAM symbiosis on P nutrition of potato.Second only to N, P is the mineral nutrient for which availability is most likely limiting to plant growth. The concentration of P in the soil solution is in the micromolar range, and moreover, this element diffuses slowly in soils. Hence, depletion of P in the root zone commonly limits further

Oxidative Stress Results in Increased Sinks for Metabolic Energy during Aging and Sprouting of Potato Seed-Tubers

“…Upon further study, we determined that PM ATPase activity in microsomal vesicles from root and tuber tissues was only half as sensitive to vanadate as that from leaf and stem tissues (Table 111). Surprisingly, data on vanadate sensitivity of ATPase in vesicles from potato tuber tissue has not been published; however, the sensitivity of ATPase in vesicles from potato roots to vanadate was reported to be only 24% (McArthur and Knowles, 1993). Our results thus agree with those presented by Berczi et al (1989) and contribute further evidence that vanadate sensitivity is not an accurate indication of PM ATPase in a11 plant tissues.…”

Influence of Species of Vesicular-Arbuscular Mycorrhizal Fungi and Phosphorus Nutrition on Growth, Development, and Mineral Nutrition of Potato (Solanum tuberosum L.)

“…Table IV shows that, although the level of shoot N was not altered by P nutrition, concentrations of soluble protein N, free amino N, and nitrate N were higher in P-deficient plants. Higher levels of such soluble N compounds in shoots reflect the slow growth and nitrate assimilation relative to N accumulation by P-deficient plants (McArthur and Knowles, 1993). Insoluble N in shoots increased linearly (P < 0.01) with increasing abiotic P supply, possibly indicating increased incorporation of soluble N into nucleic acids, imino acids, and structural N compounds, which were not detected by our assays.…”

“…3) indicated a reduction in root surface absorptive area by P stress (Newman and Andrews, 1973). Changes in the ion selectivity of roots and a diminished metabolic capacity for ion uptake have also been implicated in lower mineral nutrient accumulation by P-deficient plants (Lee, 1982;Baas et al, 1989;Rufty et al, 1990;McArthur and Knowles, 1993). Although shoot N concentration was not altered by P nutrition, N assimilation appears to be less efficient in P-deficient plants (McArthur and Knowles, 1993; Table IV).…”

Atividade ATPásica e pirofosfatásica em microssomos de raízes de milho colonizadas com fungos micorrízicos arbusculares

“…Apesar de existirem alguns relatos anteriores de ativação de H + -ATPases associada a microssomos de raízes micorrizadas (McArthur & Knowles, 1993;Bago et al, 1997;Benabdellah et al, 1999), tal ativação foi observada somente quando as atividades específicas foram calculadas com base na matéria fresca de raiz micorrizada. Entretanto, estudos citoquímicos (Marx et al, 1982;Gianinazzi-Pearson et al, 1991) indicam que a contribuição das ATPases fúngicas e, ou, arbusculares parece ser bem mais significativa em relação ao conteúdo total de proteína da raiz micorrizada do que a contribuição da massa do fungo intra-radicular em comparação com a massa vegetal para a massa fresca total da raiz micorrizada.…”

“…Krajinski et al (2002) revelaram a presença de um gene de H + -ATPases de plasmalema tecido-específico em Medicago truncatula (Mtha1), o qual é expresso apenas em células radiculares com arbúsculos. Entretanto, dados bioquímicos, quanto à regulação dessa atividade nas membranas celulares de raízes micorrizadas, ainda são escassos e, por vezes, conflitantes (McArthur & Knowles, 1993;Bago et al, 1997;Benabdellah et al, 1999).…”